Then you can download the installer from the official web (latest 64 bit Ubuntu version with IDE recommended) [1]. Once the download has finished, grant exec permission to the installer and run it. Note you must not run the installer as root:

You must accept the license agreement and then the installation button will be enabled. It is recommended to install the SDK at the default location, since installing it elsewhere can cause the IDE to be unable to find some tools (like edje_cc). Once installed, you should be able to build projects and launch the emulator.